Recent studies explore how ridehailing competes with transit, documenting drops in transit ridership when ridehailing became available. However, few examine the extent to which ridehailing substitutes for other modes, such as walking or private automobiles. Using travel diary survey data and travel times and costs from the San Francisco Bay Area, we employ a mixed logit model to analyze how trip characteristics such as travel time and travel cost influence traveler’s mode choices. The results show that if ridehailing costs increase by 10%, ridehailing trips decrease by 6.97%. About half of the lost riders would switch to driving, and 20% to transit. Therefore, driving, rather than transit, is the closest substitute for ridehailing. Furthermore, 10% reductions in transit time and transit cost are associated with a 24.63% and 5.03% increase in transit trips, respectively, suggesting that reducing travel time is more effective in increasing transit ridership than lowering fares.